Find the intersection of arrays

Return the distinct values that occur in both arrays.

JavaScript Version 1.0.0 · MIT · .md

function intersection({ left, right }) { const other = new Set(right); return [...new Set(left)].filter(value => other.has(value)); }

Input & expected output

{
  "left": [
    "[email protected]",
    "[email protected]",
    "[email protected]"
  ],
  "right": [
    "[email protected]",
    "[email protected]"
  ]
}

[
  "[email protected]"
]

The edge case

{
  "left": [],
  "right": [
    1
  ]
}

[]

Know the limits

• Result order follows the first array. Duplicate results are removed.
• Objects are compared by identity, not by their properties.
• Example: recipients that are also on a suppression list. Compare normalized addresses, and treat the provider’s suppression state as the authority.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Clone an array — Create a new array without copying the objects inside it.
• Remove duplicate values — Keep the first occurrence of each value, in its original order.
• Flatten a nested array — Turn a nested array into one sequence of values.